This article will briefly present a number of international human rights law considerations related to the topic of citizenship stripping of foreign fighters, that is: “individuals, driven mainly by ideology, religion and/or kinship, who leave their country of origin or their country of habitual residence to join a party engaged in an armed conflict”, most notably the conflict in Syria and Iraq. After that, the article will focus on considerations in the context of international humanitarian law, which have been less frequently the subject of academic debate. This contribution concludes that citizenship stripping is not only highly problematic under international human rights law, but also from the perspective of international humanitarian law. The measure – which is likely to constitute cruel, inhuman or degrading treatment or punishment – violates Article 3 Common to the four Geneva Conventions, but it also undermines accountability for international humanitarian law violations already committed and can engender new violations through the non-removal of the suspect from the conflict zone. One of the few positive sides of the connection between the measure and international humanitarian law is that even if nationality is deprived, this will not have an effect on the international humanitarian law obligation to treat that deprived person humanely. In that sense, international humanitarian law provides a welcome – albeit temporary – safety net of decent treatment for people who have become victims of countries’ refusal to take responsibility for their own citizens.